Startup device for flow-through steam generator

ABSTRACT

Device for starting up and restarting a reactor-heated flowthrough steam generator and having a relatively constantly inclined tube system traversible by feedwater in upward direction in counterflow to a gaseous heat carrier, includes a tube stringer located externally to the generator and branching off from the feedwater inlet to the tube system, a measuring element connected in the stringer for monitoring the quantity of feedwater contained in the generator, and valve means connected in the stringer and operatively connected to the measuring element and responsive thereto for controlling feedwater flow through the stringer whereby a predetermined partial filling of the tube system with feedwater is produced and maintained.

United States Patent Inventor Rupprecht Michel Erlangen, Germany Appl. No. 781,931

Filed Dec. 6, 1968 Patented Apr. 27, 1971 Assignee Siemens Aktiengesellschaft Berlin, Germany Priority Dec. 9, 1967 Germany STARTUP DEVICE FOR FLOW-THROUGH STEAM GENERATOR 6 Claims, 2 Drawing Figs.

US. Cl... 122/406 F22d 7/12 Field of Search 122/406 (S). 406(SU), 451(8), 448(5); 176/60 [56] References Cited UNITED STATES PATENTS 3,154,473 10/1964 Martin 176/6OX 3,215,126 1 H1965 Sprague 122/406 Primary Examiner--Kenneth W. Sprague Attorneys-Curt M. Avery, Arthur E. Wilfond, Herbert L.

Lerner and Daniel .1. Tick ABSTRACT: Device for starting up and restarting a reactorheated flow-through steam generator and having a relatively constantly inclined tube system traversible by feedwater in up '21. \EARTON CELL STARTUP DEVICE FOR FLOW-THROUGH STEAM GENERATOR My invention relates to device for facilitating startup and restart from cold or warm state of a once-through or flowthrough steam generator heated by a nuclear reactor. The tube system of the boiler is disposed at a continuous slope completely or at least partly in the vaporizing region in counterflow to a gaseous heat carrier such as carbon dioxide, and is traversed in an upward direction by a working medium, i.e. feedwater, for example. The parallel tubes generally pass through this region without being connected intennediately with collecting vessels or other mixing vessels.

At startup of such a boiler, one is always confronted with the problem that one cannot tell if sufficient water is contained in the boiler to be able to start the boiler feed and supply heat thereto simultaneously. Out of the fear of undue overheating, the boiler has therefore been fully supplied with water heretofore before starting to supply heat thereto. The boiler has thus always been filled with feedwater heretofore before startup or restart of the steam generator.

This startup and restart is subject to disadvantages in that large quantities of feedwater are ejected or expelled during the startup operation, consequently requiring the use of costly startup devices such as water-steam separating vessels. Moreover, the startup operation is relatively more time consuming than normal operation because a greater length of time is required for expelling the large excess quantities of water during startup operation.

It is accordingly an object of my invention to provide startup device for flow-through steam generators which avoids the aforementioned disadvantages of the heretofore-known generators, and which permits the boiler to be filled only partly with feedwater so that steam generation is effected instantaneously when heat is supplied to the boiler, and no water is expelled any longer from the boiler. Another object of my invention is to provide such startup device which dispenses with the necessity of having a water-steam separating vessel and only requires devices for supervising the water level of the boiler portions.

With the foregoing and other objects in view, 1 provide in accordance with my invention, startup device for flowthrough steam generators which comprises a measuring tube stringer located externally to the steam generator and having an inlet branching, for example, from a feedwater inlet manifold, and an outlet connected, for example, to a steam outlet manifold of the vaporizer-heating surfaces or tubes, a measuring element connected in the tube stringer for monitoring the extent to which the steam generators are filled with feedwater, and shutoff or control valves also connected in the tube stringer.

In accordance with further features of my invention, 1 provide a measuring element for sensing the amount of steam produced during startup and restart, a feedwater regulator and means for transmitting a signal from the measuring element to the feedwater regulator so as to actuate the latter to adjust the feedwater supply automatically in proportion to the increasing quantity of steam. in this way, any expulsion or ejection of water both at cold startup and also at warm startup is avoided, the boiler produces superheated steam instantaneously and feedwater regulation begins at the same time that the startup operation begins.

In accordance with other features of my invention, the regulating or shutoff valves connected in the respective measuring tube stringers are connected to a feedwater regulator and are controlled thereby so that an automatic closing and shutoff of the tube stringers is effected when the supply of feedwater to the boiler exceeds a predetermined value. For increasing output of the boiler, a greater pressure loss occurs along the vaporizer tube system due to the increasing flow-through rate or throughout of the working medium so that then a greater quantity of feedwater is forced through the bypass of the externally located measuring tube stringer which then has a lower pressure loss associated therewith. The externally located tube stringer could thus provide adequately accurate water level measurements only below a specific quantity of feedwater. If a device of the type generally known as a Barton cell is employed for measuring the filling water level, a shutoff valve can be dispensed with.

It is often desirable in reactor-heated steam generators, to subdivide the boiler into several parallel groups which are individually capable of being shut off during operation of the boiler. If such a boiler group is supposed to be shutoff, it can be advantageous to further fill this boiler portion with the aid of a demand-feeding system so that a predetermined minimum extent of filling is maintained. in accordance with yet another feature of my invention, the measuring element in the externally located tube stringer can produce and maintain this minimum feedwater volume content so that sufficient cooling of the superheater heating surfaces is assured only if the heat carrier-gas supply is unable to be completely shut off, for example, due to the fact that the flaps or valves do not close quite tightly enough.

Other features which are considered as characteristic for the invention are set forth in the appended claims.

Although the invention is illustrated and described herein as embodied in startup device for flow-through steam generator it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description when read in connection with the accompanying drawing, in which:

FIGS. 1 and 2 are greatly simplified diagrammatic views of the startup device for flow-through steam generators according to my invention, wherein the reactor and heat generator groups or boiler portions are shown respectively in longitudinal section and cross section.

In the illustrated embodiment, a CO -cooled reactor is employed. The CO; gas heated to 400 to 650 C. is conducted from the reactor core 1 in the direction of the arrows 2 to the steam generator groups or boiler portions 3 to 10. Respective circulating blowers or pumps 11 are coordinated with the individual steam generator groups. The feedwater is conducted from below through externally located inlet manifolds or collecting vessels 12 into the steam generator groups 3 to 10 having respective tube systems that are disposed at a constant inclination. Tube stringers 13 branch ofi from the inlet manifolds 12 or from other suitable locations upstream of the heating surfaces 3 proper. The stringers 13 are connected at the other ends thereof, respectively, to the steam outlet conduits l4 downstream of the heating surfaces 3. Besides regulating and shutoff valves 15, respective measuring elements 16 and 24 are connected in the tube stringers 13 and 13' respectively, that serve for supervising or controlling the extent to which the steam generator groups 3 to 10 are filled with feedwater.

Before startup of the steam generator, the boiler feed pump 18 and a boiler feed control valve 19 are actuated in response to the feedwater regulator 17 for filling the boiler with feedwater. Through the signal line 20, when a predetermined water level is attained in the boiler, a signal is passed from the measuring element 16, which supervises the extent of filling of the boiler, to the feedwater regulator 17, which cuts off further supply of feedwater to the boiler. If the gas flaps or valves for the respective boiler portion are opened and the respective circulating blower 11 is set in operation, a supply of heat is provided from the reactor 1 which produces immediate steam formation in the respective steam generator groups. The steam that is generated is sensed by a measuring element, such as a measuring diaphragm or orifice plate 21, located in the steam outlet conduit 14. The feedwater regulator 17 is actuated by the signal from the measuring diaphragm 21 conveyed thereto through the signal lead 22, so as to adjust the feedwater supply automatically in proportion to the increasing quantity of steam. If the feedwater supply exceeds a predetermined value, the feedwater regulator 17 effects a closing action of the shutoff valve through the operating line 23 so that then during nonnal operation of the boiler, the measuring tube stringer 13 is cut off.

For the partial boiler 7, the measuring stringer 13 is provided with a measuring device 24 of the type conventionally known as a Barton cell, such as is described and illustrated, for example, in US. Pat. No. 2,917,081 to C. B. Nolte, so that a shutoff valve in the measuring stringer and the control system associated therewith, are superfluous and are consequently dispensed with.

lclaim:

I. In combination with a nuclear reactor, a once-through steam generator having a tube system disposed at relatively constant inclination and traversible by feedwater in an upward direction, a feedwater inlet connected to said steam generator tube system for supplying the feedwater thereto, and means for conducting over said steam generator tube system in counterflow to the feedwater a gaseous heat carrier heated by said unclear reactor, a device for starting up and restarting said steam generator from cold and warm state, said device comprising a tube system branching off said feedwater inlet and located externally to said steam generator, and means located externally to said steam generator for monitoring the quantity of feedwater contained in said steam generator and for controlling feedwater flow through said external tube system so that the steam generator is only partially filled with feedwater.

2. Device according to claim 1, wherein said last-mentioned means comprises a measuring element connected in said external tube system for monitoring the quantity of feedwater contained in the steam generator, and valve means connected in said external tube system and operatively connected to said measuring element and responsive thereto for controlling feedwater flow through said external system.

3. Device according to claim 1 including measuring means connected in a steam outlet of said steam generator tube system in proportion to the increasing quantity of steam produced therein.

4. Device according to claim 2, including feedwater-regulating means connected to said feedwater quantity-measuring element and to said valve means, said feedwater-regulating means being responsive to a signal from said feedwater quanti' ty-measuring element indicating that the quantity of feedwater supplied to the generator exceeds a predetermined value for automatically closing said valve means.

5. Device according to claim 1, wherein said last-mentioned means comprises a Barton cell.

6. Device according to claim 2, wherein the steam generator is subdivided into a plurality of parallel groups, means for individually shutting off feedwater to each of said parallel groups during operation of the steam generator and means for demand-feeding a shutoff group of the steam generator with feedwater to a predetermined minimum feedwater quantity monitored by the respective feedwater quantity-monitoring means. 

1. In combination with a nuclear reactor, a once-through steam generator having a tube system disposed at relatively constant inclination and traversible by feedwater in an upward direction, a feedwater inlet connected to said steam generator tube system for supplying the feedwater thereto, and means for conducting over said steam generator tube system in counterflow to the feedwater a gaseous heat carrier heated by said unclear reactor, a device for starting up and restarting said steam generator from cold and warm state, said device comprising a tube system branching off said feedwater inlet and located externally to said steam generator, and means located externally to said steam generator for monitoring the quantity of feedwater contained in said steam generator and for controlling feedwater flow through said external tube system so that the steam generator is only partially filled with feedwater.
 2. Device according to claim 1, wherein said last-mentioned means comprises a measuring element connected in said external tube system for monitoring the quantity of feedwater contained in the steam generator, and valve means connected in said external tube system and operatively connected to said measuring element and responsive thereto for controlling feedwater flow through said external system.
 3. Device according to claim 1 including measuring means connected in a steam outlet of said steam generator tube system in proportion to the increasing quantity of steam produced therein.
 4. Device according to claim 2, including feedwater-regulating means connected to said feedwater quantity-measuring element and to said valve means, said feedwater-regulating means being responsive to a signal from said feedwater quantity-measuring element indicating that the quantity of feedwater supplied to the generator exceeds a predetermined value for automatically closing said valve means.
 5. Device according to claim 1, wherein said last-mentioned means comprises a Barton cell.
 6. Device according to claim 2, wherein the steam generator is subdivided into a plurality of parallel groups, means for individually shutting off feedwater to each of said parallel groups during operation of the steam generator and means for demand-feeding a shutoff group of the steam generator with feedwater to a predetermined minimum feedwater quantity monitored by the respective feedwater quantity-monitoring means. 